This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
Rotary drums are designed and manufactured in varying diameters in response to throughput, materials, temperature, and a variety of other engineering parameters To accommodate the varying diameter drums, varying diameter end housings must be designed to allow the drums to penetrate the end housings with a minimal gap as to accommodate future eccentricity, or out of roundness of the drum.
To seal this gap, one such method, like U.S. Pat. Nos. 5,571,269 (Buelow) and 4,405,137 (Webb), is to have a framework of overlapping seal flaps which are formed to an angle such that one edge of the seal flap 6 is clamped tightly to an annular ring which is affixed securely to the stationary end housing. The annular ring typically has mounting studs welded into the conical section of the ring which are used to affix the seal flaps through mounting holes adjacent a mounting edge of the seal flap. Past designs of this flap provided for a round mounting hole and slotted mounting hole. The slotted mounting hole has allowed for a sealing assembly with a fixed number of seal flaps to accommodate a small range of drum diameters before having to add or subtract a seal flap from a total number of seal flaps needed to make a seal. For instance, a 100-inch outer diameter drum would require 50 seal flaps to affect a proper seal. The slotted mounting hole would increase the range of diameter from just 100 inches specifically, to 98-102 inches. The slotted mounting hole allows for some standardization in seal flap design such that it accommodates a shorter or longer chord length between the mounting studs in the annular ring. Standard sized seal flaps can be made to fit a varying range of drum diameters by simply adding or subtracting several seal flaps to accommodate 360-degree coverage of the rotating drum.
The seal flaps have been further standardized into 4 different size seal flaps to accommodate drum diameters as small as 2 feet, and as large as 20+ feet. With each size of seal flap, the leading mounting hole has traditionally been round. The issue with this, that this invention addresses, is that the round hole limits the range of diameters that each of the seal flaps can be used. By traditional design, the top edge of the seal flap is not in parallel with the wear shoe edge of the seal flap to accommodate how the seal flaps arc mounted. Since the seal flaps are swept in design, the tangential line from where the wear shoe would contact the rotating drum is not in parallel with the tangential line from where the clamping edge of the seal flap mounts to the annular ring. As the tapered top edge of the seal flap addresses mounting, the round mounting hole limits the range of diameters that a given seal flap can effectively mount to. For instance, a smaller size seal flap is needed due to space constraints on the sealing surface of the rotating drum where a seal is to be mounted. Since the degree of taper is fixed on the mounting edge of the seal flap, it may not accommodate a much flatter profile of a larger drum having the tangential lines of the sealing surface and annular mounting rings being much closer to parallel than what a smaller diameter drum might have for which the smaller seal flap was originally designed. The distance between the mounting hole and a wear pad hole are fixed for a seal flap, and as the tangential lines between the sealing surface and mounting studs become more parallel, the stud placement for the mounting hole drops toward the wear pad hole, which causes excess material to become available along the interior edge and creates a bulge in the seal flap between the mounting hole and the wear shoe. This opening of the overlap joint greatly reduces the efficiency of the sealing arrangement.
Wear shoes are affixed by typical nuts and bolts hardware to the other edge from the mounting edge of the seal flap that contact the rotating drum at the sealing surface. Wear shoe holes arc used for affixing the wear shoe to the seal flap. Seal flaps, each having an affixed wear shoe at the end, arc overlapped such that the wear shoes are abutted together. A slotted hole 26 adjacent the sealing edge and the wear shoe hole 27 is used for overlapping the seal flaps together and is positioned over a wear shoe hole. This slotted hole 26 has been traditionally slotted to accommodate seal flap movement in response to eccentricity in the rotating drum as it ages and becomes oval or out of round.
The wear shoes are held in contact with the rotating drum by 1; the tension of the seal flap springing back toward the drum surface due to flexure and 2; a tension cable assembly (consisting of a cable, loop thimbles, cable clamps, extension springs, and cable binders) which are laced through eye nuts that help affix the wear shoes to the seal flaps. The seal flaps are overlapped around the rotating drum whereas edge 25 is tucked underneath edge 28 in the seal flaps to provide complete coverage of the open gap between the end housing and drum.
This sort of arrangement, like U.S. Pat. Nos. 5,571,269 (Buelow), and 4,405,137 (Webb), traditionally uses a steel sintered wear shoe to prevent the edge 23 of the seal flap from scoring the scaling surface of the rotating drum. The wear shoes arc abutted together with small inherent gaps between the abutments. These wear shoes are very heavy and prior to installing the tension cable, may cause the sealing segments to sag away from the bottom portion of the drum as the weight of the sintered shoes overcome the tension provided by the seal flaps. Thus, extra tension is required by the tensioning device to pull up the bottom part of the seal to contact the drum sealing surface. As the bottom of the seal is only making the necessary contact with the sealing surface, the top and sides of the seal now have extra undue force pushing the wear shoes into the scaling surface. Essentially the top and sides of the seal arc now supporting the weight of the sintered wear shoes at the bottom of the seal. This extra tension and weight results in a shorter lifespan for the wear segments of the seal.
As equipment and seals age, they inevitably become more out of round which causes gaps to open between segments of any type of overlapping scaling system. As the rotating drum runs in and out from a true rotational axis, the sealing segments must conform to the movement of the drum. Overlapping seal flaps, and inevitably the wear shoes must expand as the drum runs out. This opens gaps between overlapping seal flap segments and between the abutting wear shoes. These open gaps cause seal efficiency to drop.